1. Field of the Invention
The present invention relates to: an image processing apparatus such as a multi-function peripheral (MFP), i.e., a multifunctional digital image forming apparatus; an image processing method for the image processing apparatus; and a non-transitory computer-readable recording medium storing an image processing program for the image processing apparatus to implement the image processing method.
2. Description of the Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
There is a high-speed scanner for image processing apparatuses and once such a high-speed scanner starts image input, it cannot stop the operation until it is finished. Therefore, in preparation for image input, it is necessary to reserve a memory area equivalent to one page of compressed and encoded image data in a memory.
There are the following types of memory for image processing apparatuses: a main memory that allows free accesses from a CPU and can be expanded with extra memory as the need arises; a sub memory that allows only direct memory accesses (DMA) and has as much memory area only as the device configuration needs; and a non-volatile backup memory device for storing great size of encoded data.
Main memory is more expensive than sub memory because of its optional feature, i.e., memory expansion. In order to reserve a band wide enough for image transfer, a configuration needs to be made such that a main memory and a sub memory are accessed through different channels.
When a memory area equivalent to one page of image data is reserved in a main memory, a scanner can perform quick image inputs with an automatic document feeder installed thereon. Since the performance of an automatic document feeder determines the size of a memory area to be reserved in a main memory, it is very common to expand a main memory with extra memory for quick image inputs.
For example, there are image processing apparatuses provided with a dual scan-enabled automatic document feeder; some of them are configured to reserve a memory area equivalent to four A3 sized pages of image data in their main memories. There are other image processing apparatuses provided with a normal automatic document feeder; most of them are configured to reserve a memory area equivalent to two A3 sized pages of image data in their main memories.
Being provided with an expanded main memory, such an image processing image apparatus can reserve a memory area for storing image data quickly and the automatic document feeder can perform a quick document scan. Also, image data can be decompressed quickly from the expanded main memory in preparation for image output. That is, a quick image input and output can be performed concurrently.
In contrast, cost-saving image processing apparatuses must be provided with a main memory of a small size. When a memory area equivalent to one A3 sized page of image data can be reserved in a main memory, the main memory is of a size as small as possible.
After one page of image data input from a scanner is stored on a main memory of a small size, image input on a next page cannot be started unless a backup copy of that page is stored on a backup memory device. While performing image input, image data cannot be read out from the backup memory device in preparation for image output, which negatively and significantly affects its performance.
As a solution to the problem, a sub memory having a paging buffer can be employed. With such a sub memory, a backup copy of encoded data can be stored band by band on the backup memory device quickly and image input on a next page can be started quickly. Furthermore, a memory area for storing image data page by page can be reserved quickly in the main memory of a small size and thus image data can be obtained quickly from the backup memory device in preparation for image output. That is, quick image inputs and outputs can be performed concurrently without the need for a main memory of a large size.
As described above, an image data input method implemented for the image processing apparatus provided with the main memory of a small size includes: reserving a memory area capable of storing image data page by page in the sub memory when image data is input from the scanner, for example; temporarily storing encoded image data from the sub memory band by band on the main memory; further storing a backup copy of the encoded image data on the non-volatile backup memory device; deleting the same from the main memory; and reserving a memory area for storing image data page by page in the main memory in preparation for image output.
Japanese Unexamined Patent Publication No. 2006-020029 discloses: an image input and output device provided with an image output portion that cannot stop its operation until it is finished, which is characterized by reserving a memory area for storing encoded data page by page in its encoded data memory and reserving memory area for storing bitmap data band by band in its bitmap data memory; and an image input and output device provided with an image output portion that can stop its operation while it is active, which is characterized by reserving a memory area for storing encoded data band by band in its encoded data memory and reserving memory area for storing bitmap data band by band in its bitmap data memory.
The above-described image data input method, which includes: reserving a memory area capable of storing image data page by page in its sub memory; temporarily storing image data band by band on its main memory; and reserving a memory area for storing image data page by page on its main memory in preparation for image output, can be implemented for an image processing apparatus provided with such an image input and output device as well as a main memory of a small, which causes the following problem.
The size of memory areas to be reserved in the main memory and the sub memory is determined such that the memory areas can store maximum sized pages of image data. In other words, it is determined such that the maximum level is guaranteed, which may cause a large free memory area in the main memory and the sub memory depending on the image processing mode. For example, when a low-resolution image is input, only a small memory area for storing image data page by page is reserved and a large free memory area may be left in the main memory and the sub memory.
In this case, an alternative image data input method, which includes reserving a memory area equivalent to one page of image data in the main memory, can be implemented for quick image inputs. Despite the presence of the alternative, it is really wasteful that the image input and output device cannot make full use of its resources in the image data input method, which includes: reserving a memory area for storing image data page by page in the sub memory; reserving a memory area for storing image data band by band in the main memory; and storing a backup copy on the backup memory device.
Japanese Unexamined Patent Publication No. 2006-20029 does not teach any technique that can bring a solution to the above-described problem.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.